A fluid turbine flow meter includes a casing comprising a measurement chamber into which lead an inlet pipe and an outlet pipe and a turbine having blades and driven in rotation in the measurement chamber by the jet of fluid entering via the inlet pipe and acting on one or more blades.
The fluid turbine flow meter also includes a casing containing a counter for counting the number of turns of the turbine, to which the latter is coupled by a magnetic transmission in the case of a dry counter and by a mechanical transmission in the case of an immersed counter, and a transparent cover covering the counter.
A problem currently encountered in the case of velocity turbine meters resides in the fact that at low flow rates the inactive blades that are not driven by the jet of fluid entering the measurement chamber, in other words that are not subjected to the driving thrust of the fluid, slow down the turbine.
In particular, when the fluid turbine flow meter is operating at a low flow rate, because of the low velocity of the flow the turbine is slowed down and the performance of the meter in terms of flow rate measurement is reduced.
There exists a requirement to find a technical solution that would make it possible to reduce measurement errors at low flow rates by limiting the hydraulic braking effect of the movement of the inactive blades in the fluid at the same time as preserving a maximum driving force when the jet of fluid impinges on the active blade or blades.